1. Field of the Invention
The present invention relates to a detachment prevention device of a seat rail for a vehicle, and more particularly, to a detachment prevention device of a seat rail for a vehicle, designed to prevent upper and lower rails constituting the seat rail from being detached from the seat rail by virtue of impact (inertial force) occurring when external force is applied to the seat rail in the event of a crash or the like.
2. Description of the Related Art
Vehicle seats serve to maintain the posture of a passenger in a vehicle, and may be classified into a driver seat, a driver-side passenger seat, and a rear passenger seat.
A seat rail serves to mount the vehicle seat, and has a buckle for fastening a seat belt fixed to one side thereof (an inner surface of the seat rail, and more specifically, the right side of the seat rail in the case of the driver seat, and the left side of the seat rail in the case of the driver-side passenger seat). Accordingly, when a passenger is seated in the vehicle with their seat belts fastened and a sudden stop or a crash occurs, a significant inertial force is applied to the seat rail, thereby causing the vehicle seat to be detached from the seat rail.
In particular, when the passenger is seated in the vehicle with their seat belts fastened, the weight of the passenger is added to the inertial force of the impact, and is then transferred to the seat belt together with the inertial force, so that if the crash occurs in the case where the buckle for fastening the seat belt is fixed to an inner surface of the seat rail, the seat rail is subject to a serious deformation.
With reference to FIGS. 1 and 2, the construction of the seat rail and deformation thereof when a load is applied to the seat rail will be described as follows.
A seat rail 30 for a vehicle generally includes a lower rail 33 fixed to a vehicle body by means of fixing means, such as rivets or bolts, and an upper rail 34 located on the lower rail 33 and coupled thereto.
The lower rail 33 and the upper rail 34 are bent at both ends thereof to form bent portions 35, respectively, such that the lower rail 33 can be hooked to the upper rail by means of the bent portions 35. The upper rail 34 has a bracket 37 extended from the center of the upper rail 34 to an upper portion thereof to fix the seat 36 to the upper rail 34.
The bracket 37 has a buckle 38 fixed thereto for fastening the seat belt.
In such a construction, when an impact force is transferred to the seat rail in the event of a crash or the like, the force is focused more on the inner portion of the seat rail, to which the buckle for fastening the seat belt is fixed, than any other portions of the seat rail, so that the inner portion of the seat rail is deformed and is then detached from the seat rail.
Specifically, among components of the inner portion of the seat rail to which a greater load is applied than any other portions, the upper rail 34 is subject to an upward force and is then lifted together with the seat 36, whereby an outer portion OP of the fixing means 32 for fixing the lower rail 33 is deformed (elongated) at first, and then the bent portions 35 of the upper and lower rails 33 and 34 are deformed.
If the outer portion OP of the lower rail 33 is deformed, an inner portion IP of the lower rail 33 is also deformed, but the deformation of the inner portion IP is not serious, compared with the outer portion OP.
At this time, the first deformation occurs at an outer side wall OSW of the lower rail 33 on the outer portion OP of the lower rail 33, followed by deformation of the bent portions 35. A deformed length of the outer side wall OSW is limited from an end point EP of the fixing means 32 to the bent portion 35 of the lower rail 33, which causes a rapid deformation of the bent portions 35, resulting in detachment of the seat rail.
The detachment of the seat rail as described above can cause the passenger to be ejected out together with the vehicle seat, and causes a secondary impact of the passenger against the interior of the vehicle, such as a window or an instrument panel, thereby causing serious problems, such as aggravation of injury to the passenger and the like.